Add `edit` endpoint for Release page

What does this MR do?

This MR provides the BE that's necessary to access the Release Edit page. A new route will be added in order to access this page. Here's an example of what it'll be:

http://localhost:3000/<namespace>/<project>/-/releases/<release-tag>/edit

Feature Flag

This feature is built behind release_edit_page feature flag.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry => Behind release_edit_page feature flag
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers

Related: #26016 (closed)